Microstructure investigation of 5754 aluminum alloy welded with FSW process

Abstract

The thesis investigates how three metallographic etching reagents which include Keller's reagent, Barker's reagent and Weck's reagent affect the ability to interpret the microstructure of AA5754 aluminum alloy that was welded through the friction stir welding process. The study investigates how well each reagent uncovers specific weld zones that include the nugget zone and thermo‑mechanically affected zone and heat‑affected zone while testing their ability to show grain boundaries and material flow patterns. Weld samples were prepared under controlled conditions and applied all three reagents for etching to assess how well each reagent defined structural elements and created contrast for studying microstructures. The study demonstrates that the reagents produce distinct results to show weld zones where some reagents better show the weld zones and stirring patterns and others don’t show any change at all. The research shows that the choice of the regent can determine how accurately FSW microstructure can be analyzed, making it easy to identify the problems in the weld and weld defects. Optical microscope and electron scanning microscope were used to analyze the sample after metallographic preparation and etching and a decision was made depending on the images given by the microscope. This research shows that choosing the right etching reagent is vital for precise microstructure examination of FSW aluminum alloy which leads to identification of any weld defects.